Method for producing basic products for use as e.g. alkalizing agent (soda lye substitute), for ground stabilization or as filler/pigment

ABSTRACT

A method for producing basic products from ashes, minerals, organic solids and other solids, including the provision of a starting material in particle form, mixing the starting material with an additive for synthesis and crushing the particles of the starting material, with a modification of the particles by the supplied additives for synthesis taking place directly during crushing, such that the energy-efficient production of a basic product with a defined particle size and high reactivity is effected and the produced basic products can be used directly for further product production, e.g. as alkalizing agent, for ground stabilization or as filler/pigments.

TECHNICAL FIELD

The present invention relates to a method for producing basic products for use e.g. as alkalizing agent (soda lye substitute), for ground stabilization or as filler/pigment. The starting materials can be ashes, calcined basic products, minerals, organic solids and other solids such as pigments and fibers, plastic, rubber, etc.

In particular, the method relates to the energy-efficient recycling and defined modification of power station ashes, mineral substances such as marble and solids for further product production.

BACKGROUND

Substances such as industrial ashes and incineration ashes have so far been passed on mainly as waste for utilization primarily to the building and cement industries. DE 10 2005 029500 A describes, however, that by the indirect use of the high alkali and alkaline earth oxide contents a substitution of soda lye by recycled ash as alkalizing agent is used in paper recycling and in wood pulp bleaching.

Owing to the material properties of starting materials such as ashes, which have a large proportion of important components such as CaO, MgO, Al₂O₃ and Na₂O, the recycling of waste products to basic products that can be reintroduced into industrial processes e.g. in paper and wood processing, in ground stabilization or as filler/pigments is of economic and ecological interest.

Processing is, however, necessary inter alia since, due to their particle size, the starting materials negatively impact the course of processes. For the recycling of starting materials such as industrial ashes and incineration ashes, inorganic or organic solids as well as minerals, conventional methods have so far been used, in particular milling in a wet process with conventional milling machines such as ball mills. However, the recycling of these starting materials has been uneconomic so far due to the high amount of energy required.

A further problem of the conventional milling methods is, however, that in particular in the wet process technical problems and high downtime often arise, which are caused by the abrasive wear of the milling tools, deposition and/or cakings in the milling zone or blockings of the plant.

This problem is aggravated considerably when using hygroscopic materials such as ashes or calcined basic products, which tend to form agglomerates, or even makes recycling of these substances impossible.

A further problem of the conventional wet processes is that they take place under atmospheric conditions, in which air induction into the milling zone can hardly be prevented and therefore a reverse reaction (reagglomeration) of the particles takes place directly during milling. This reverse reaction results in an increased formation of agglomerates so that a defined particle size with a homogeneous size distribution of the basic products cannot be achieved at present or can only be achieved with a high expenditure of energy e.g. by further process steps. In particular, it is disadvantageous that due to the reverse reaction the newly created surfaces of the particles at the same time lose their reactivity.

The basic products produced according to conventional methods therefore have a low quality and can only be reintroduced into industrial processes to a limited extent.

These circumstances have so far prevented efficient recycling of a plurality of starting materials for use as a marketable basic product and further processing thereof to an end product.

DESCRIPTION OF THE INVENTION

Against this background, the invention provides a method that enables the production of basic products, which have a defined particle size with a homogeneous distribution and a high reactivity and which can therefore be integrated in industrial processes, without requiring a high amount of energy that makes the use uneconomic.

The present invention is based on the idea to carry out an energy-efficient crushing of particles, in which directly before the crushing the particles are mixed with a specific dosage of an additive. It is assumed that the particles freshly broken up by the crushing have the largest possible surface as well as the highest possible number of reactive surface areas at the time of crushing and enter a spontaneous reaction on site, i.e. in situ, with additives for synthesis. In this regard, it is supposed to be prevented that due an uncontrolled reaction at the resulting surface a reverse reaction (reagglomeration) takes place. It is further assumed that with the method according to the invention controlled, application-related properties of the basic products, which can also be used for a specific secondary reaction such as crystallization, are achieved.

Through intensive studies, the inventors have developed a method that is suited for the energy-efficient production of high-quality basic products having a defined particle size.

In this regard, the average particle size for dry particles is determined according to ISO 13320 and for wet particles according to the sedimentation method using x-ray absorption of a usually aqueous slurry containing the product, which is usually set to a measurable consistency by dilution with ethanol to prevent the dissolution of small particles.

Typically, an average density of 3.0 g/cm³ is used for ash, and for the liquid phase owing to the strong dilution the data of ethanol (density 0.7764 g/cm³, viscosity 0.9144 mPa·s) are used.

The method will be described in more detail below.

Within the scope of this invention, reactivity is understood as the ability of a substance to enter a spontaneous reaction or a bond at its surface with the medium in which it is located. The larger the reactive surface, the greater the reactivity of a substance.

Within the terms of the present invention, reverse reaction (also designated as reagglomeration) is understood as a process, in which a substance loses the state brought about by the milling process directly after the milling process. In a reverse reaction, surfaces generated by the milling process for instance can lose their activity e.g. by reaction with the milling medium or by repeated formation of agglomerate.

In the method according to the invention, the starting materials are provided in an aqueous solution, e.g. as suspension, dispersion or emulsion, or in the dry state, with the possibilities described in FIG. 2 e.g. to regulate the pressure, the temperature or the dry content of the starting materials and to add additives such as carbon dioxide or reagents to the starting materials.

Preferably, provision is in the dry state, with the setting of the temperature and/or the dry content taking place e.g. by circulation of the starting material by means of a blower. For this purpose, the starting materials are provided in air or an air/gas atmosphere, CO₂-containing gases being preferably used.

The starting materials are all starting materials in particle form, the method according to the invention being suited in particular for hygroscopic starting materials.

In particular, starting materials can be recycled, which are selected from one or more calcined basic products, inorganic substances, organic substances, mineral substances and ashes, in particular paper ashes.

The ashes comprise all types of incineration ashes and industrial ashes, particularly preferred ashes being such ashes which have a high content of CaO, MgO, Al₂O₃, Na₂O such as e.g. paper ashes or wood ash with a low inert content (e.g. SiO₂) and/or a low heavy metal content. According to the invention, the paper ashes comprise ashes from the recycling of paper/paperboard and their residual substances as well as residues e.g. after thermal aftertreatment. According to the invention, the ashes further comprise ashes from burning processes, which developed at a temperature below or over 850° C. Furthermore, the ashes can be present preferably in a suspension with water.

The starting materials furthermore also comprise mineral substances, inorganic and/or organic solids. Inorganic substances comprise preferably calcined substances, which are burnt or reburnt, particularly preferably marble or calcined clay. Organic substances comprise preferably pigments, fibers, plastic, rubber, beans and other solids. Mineral substances comprise preferably unburnt, burnt or sintered mineral substances, particularly preferably marble, clay or clay-containing substances, calcium oxide, calcium hydroxide, magnesium oxide and substances containing these minerals. The starting materials according to the invention can also be mixtures of two or more of the above-stated starting materials, as listed in FIG. 2 under starting materials. Mixtures with ashes are preferred.

The starting materials are provided in particle form, according to the invention the provision of a substance in particle form meaning a starting material in the form of a particle of any morphology, preferably the particles have an average particle size from 0.01 μm to 10 mm, particularly preferably from 0.1 μm to 10 mm and even more preferably from 0.1 μm to 1 mm, the average particle size for dry and wet particles being determined as described below in connection with the separation into fine and finest fractions.

Preferably the particles of the starting material are optionally supplemented with additives such as CO₂, CO₂-containing gases or reagents and precrushed to obtain predetermined breaking points and hairline cracks, by which the method according to the invention becomes more efficient in the use of energy and the crushing of the particles.

In FIG. 2, this option is illustrated in that the additives are added to the starting materials before the starting materials are subjected to precrushing.

The crushing of the particles of the starting materials is carried out in both a dry as well as a wet manner by counterrotating rotors with specific internals depending on the material to be milled. By this, high-frequency pressure impulses, (e.g. with a frequency greater than 8 kHz) are created in a high frequence pressure impulse crusher (hereinafter designated inter alia as HFPI or as HFPI crusher) with undirected pressure impulses, in a dry manner preferably under a high airflow, in a vibration-transmitting medium, which is followed by an in situ separation, as designated in FIG. 2 as “HFPI crusher with in situ separation”.

In the HFPI crusher, the crushing of the particles of the starting material is carried out in a non-contact manner by pressure waves. High-frequency impact pressure fronts, e.g. with a frequency greater than 8 kHz, are understood as pressure waves or also pressure impulses. By using pressure waves, natural frequency disintegrations, crystal water disintegrations and interactive stimulation of oscillation between the particles contribute to crushing and increasing the microporosity of the material to be milled. The crushing by pressure waves takes places in a vibration-transmitting medium.

Such a non-contact milling or disintegration process is described, for instance, in DE 102 59 456 A1, in which impact pressure fronts (pressure waves) with an impulse duration of less than 10 μs and a subsequent frequency of greater than 8 kHz strike the particles. In this process, the subsequent frequency can vary. For further details, reference is made to DE 102 59 456 A1.

A further process for crushing is described, for instance, in WO 91/07223, which is preferably suited to be able to crush particles in a wet manner.

Vibration-transmitting media are liquids such as e.g. water, water-solvent mixtures, in which one or more solvents are optionally emulsified, as well as solvent mixtures of two or more solvents, mixtures of air or air/gas. Particularly preferred media are mixtures of air, air/gas and/or gas in any combination, preferred are air/gas mixtures with CO₂-containing gases. If CO₂ is contained, it is possible to protect the particles from a reverse reaction by passivation. The crushing of the starting materials is carried out preferably in the dry state and in particular under high airflow.

The execution of the HFPI crushing in the dry manner as well as in the wet manner can be carried out in one step or in several steps, several steps in that the HFPI crushing is carried out in several HFPI crushers connected subsequently in a row or in a cascade.

Furthermore, additives are optionally added before, during or after the crushing, which either directly react with the particles or which protect the particles e.g. by passivation. The additives are in particular one or more gases or concentrated gases, preferably carbon dioxide containing gases, particularly preferably CO₂-containing waste gases and flue gases from e.g. thermal power stations, steam power stations and biogas plants. Similar to that stated above, the addition of carbon dioxide containing gases or the addition of, for instance, carbon dioxide containing gases concentrated from waste gases results in the protection of the particles from a reverse reaction. Moreover, it is advantageous in terms of environmental technology to use the waste gases and flue gases from thermal power stations, steam power stations and biogas plants, which would otherwise have to be elaborately purified, for this purpose.

If the crushing is carried out in a dry manner, preferably moist, CO₂-containing gas or moist, concentrated CO₂-containing gas are used as additives to use the high reactivity of the new surfaces and to prevent reverse reactions.

Furthermore, the particles crushed in the HFPI crusher can optionally be used directly for further processing in their present state or preferably in a dispersion, as designated in FIG. 2 as “for further processing”. A dispersion is preferably prepared by feeding the particles into a dispersing medium without induction of foreign air or foreign gas. Precrushing in the HFPI crusher is particularly energy-efficient, and therefore the energy balance of the method according to the invention in combination with the HFPI crusher is particularly favorable. Due to precrushing, the reaction times in the method according to the invention are moreover shortened, which results in a potentially higher throughput.

Furthermore, in a directly subsequent step, the particles crushed in the HFPI crusher are separated in situ into at least two fractions which are different in the average particle size.

Within the scope of this invention, “in situ” is to be understood as the separation of the particles directly subsequent to the crushing. This means that there is no procedural gap between the crushing of the particles and the separation. This has in particular the advantage that the individual fractions can be directly used for further processing without further processes reducing the reactivity of the basic products.

In the dry process, the separation in an energetic process is possible without additional energy for a separate module being necessary (since it is in the same airflow). The dry HFPI process generates a high air through-put in the particle crushing. This airflow is used in situ to separate the fine particles in the subsequent separation in the cyclone (after the expansion of air/pressure removal). The airflow is subsequently recycled. In a separate module (e.g. air separator), on the other hand, the airflow required for this would have to be additionally generated.

An immediate and separate storage of the ashes and products is possible. In this case, the separation is carried out before a possible interaction (reagglomeration) after the HFPI crusher without additional filtering. A dispersant or separating agent can be added in this process as support. The cleaned product of the ash cooler filter can, depending on the requirements, be added optionally before the HFPI crusher or directly to the coarser Cinerit fraction (the term “Cinerit” will be explained later).

A further advantage is that the applied temperature can be held and, if necessary, be used for a further production (modification) step e.g. in a moist medium, without additional energy having to be supplied. Since the airflow is recycled, no (cold) fresh air has to be supplied that causes cooling of the product. Here, on the other hand, a subsequent process e.g. in situ synthesis crushing (hereinafter also abbreviated as ISC) or alkalization with warm ash can be carried out. Cooling happens only when the ash is removed from the system (e.g. by storage in the silo).

The separation is carried out e.g. via a cyclone, preferably via a cyclone with air recycling. Optionally, e.g. additional air separators are used to enable a further separation of the particles into additional fractions.

For the in situ separation of the particles crushed in a wet manner, preferably separating units, so-called gravity separators, are used which make use of the centrifugal or gravitational forces. Examples of such separating units are hydrocyclones (cleaners), centrifuges or (upstream) classifiers.

Optionally, additives are added during the separation, which are selected from the above-stated additives according to the invention. Preferred additives are CO₂-containing gases or gas mixtures, preferably CO₂-containing waste gases or flue gases. A concentration of CO₂ from flue gases and waste gases from biogas plants is preferably used for some processes (CaCO₃ formation).

To prevent foreign air induction, the entire system for the reproduction of the method according to the invention is closed. Pressure variations are optionally balanced by filter elements. Pressure, temperature, degree of dryness and atmosphere are optionally and continuously controlled in the method according to the invention to optimize the production of the basic products.

The above-described separation is carried out preferably into a first fraction, the finest fraction, which has an average particle size in the range from 0.1 to 8 μm and a second fraction, the fine fraction, which has an average particle size in the range from 8 to 100 μm.

In connection with the separation into the fine and finest fractions as well as in the entire described method, the average particle size for the dry particles and/or the basic product is measured according to ISO 13320. In this case, the determination of the particle size is based on the physical principles of laser diffraction. In particular, the HELOS analyzers developed by Sympatec are used in combination with the RODOS dry dispersing unit and operated according to the manufacturer's instructions (Sympatec GmbH, Augsburg, Germany).

For the determination of the average particle size for the wet particles and/or the basic product, the sedimentation method is employed using x-ray absorption of an aqueous slurry containing the particles, which is usually set to a measurable consistency by dilution with ethanol to prevent the dissolution of small particles. Typically, an average density of 3.0 g/cm³ is used for ash, and for the liquid phase owing to the strong dilution the data of ethanol (density 0.7764 g/cm³, viscosity 0.9144 mPa·s) are used. The particle sizes can be determined in particular by means of a Sedigraph 5100 of Micromeritics, U.S.A. For more detailed information, reference is made to the operator's manual (Micromeritics, Sedigraph 5100, Particle Size Analysis System, Operator's Manual v3.07, 1994).

The fractions obtained in the separation are optionally resupplied to the crushing step as often as desired, as designated in FIG. 2 as “x-fold recycling”.

The obtained fine and finest fractions are optionally used directly as basic product in the further product production e.g. as Cinerit® or Elurit®. These basic products are designated as basic products 1+2 in FIG. 2. The basic products 1+2 can be mixed with other basic products, which is preferably carried out in a dispersion without induction of foreign air or foreign gas.

To indicate that the fine and finest fractions can, independent of each other, provide the respective basic product, the basic products according to the invention are respectively designated with two numbers, here “1+2”.

Within the scope of this invention, Cinerit is understood as the basic product obtained in the fine fraction; Elurit is understood as the basic product obtained in the finest fraction. In this case, the finer fraction is separated from the coarser fraction by in situ air separation in the process without requiring additional energy in the circulating flow (same airflow).

There is also the option to unite the starting materials directly with the particles of the fine and finest fractions produced in the method according to the invention and thus to avoid the HFPI crushing with in situ separation, as designated in FIG. 2 as “avoiding HFPI”.

For the method according to the invention, the pretreated particles are preferably provided in an aqueous slurry. In this case, aqueous slurries, so-called dispersions, are prepared in that the pretreated starting materials are fed into an aqueous medium optionally without induction of foreign air or foreign gas. The slurries can optionally also contain stabilizers e.g. citric acid, dispersants e.g. polyacrylates, polyphosphates or polycarbonates, solvents and solvent combinations, e.g. of alcohols, preferably of ethanol, isopropanol, alkoxypropanols, of ketones, preferably acetone, of amines, preferably triethylamine as solvent and anticorrosive, or of silanes and siloxanes in benzine or isoparrafin.

The thus provided starting materials are mixed with at least one additive for synthesis and are supplied to directly subsequent crushing. This crushing is carried out in an in situ synthesis crusher (ISC), in a step as designated in FIG. 2 as “in situ synthesis crushing”.

According to the invention, “in situ synthesis crushing” is understood as the crushing of the particles and the reaction of the thus newly created, reactive surfaces with the previously added additives for synthesis on site.

The step of in situ synthesis crushing can comprise wet milling or dry milling, preferably wet milling. Furthermore, the in situ synthesis crusher can optionally be followed by a downstream reactor and/or crystallizer.

Any gases, aerosols, liquids and/or solids are suited as additives for synthesis, preferred are such that contain carbon dioxide, hydrogen fluoride, hydrogen carbonate, hydrogen bicarbonate, alkylalkoxysilanes or bleaches such as e.g. H₂O₂ or sodium dithionite or a mixture thereof. Particularly preferred additives are CO₂-containing gases, concentrated gases or gas mixtures, preferably CO₂-containing waste gases or flue gases. The additives for synthesis can be variably dosed to control the processes such as chemical changes, settings of the pH value and phase mixtures.

In the method according to the invention, one or more additives selected from citric acid, polyacrylates, polyphosphates, polycarbonates, alcohols, in particular ethanol, isopropanols, alkoxypropanols, ketones, in particular acetone, amines, in particular triethylamine, silanes and siloxanes in benzine or isoparrafin, sulfuric acid, sulfates, in particular lignosulfates, alums, in particular aluminium sulfate, phosphoric acid, phosphates, soluble metallic salts, calcium oxide, calcium hydroxide and magnesium oxide can be added to the additives for synthesis at any point.

Furthermore, metallic salts can be used in particular for controlling the crystal structure.

The added reagents can also serve to provide reaction options such as crystallizations, preferably H₃PO₄ being added for the precipitation of calcium phosphates, lignin sulfonates for the precipitation of calcium lignin sulfonates and alums such as aluminium sulfate for the precipitation of calcium aluminium sulfate (Ca(Al₂[(OH)₂(SO₄)₂]x 26 H₂O).

Particularly preferred additives are excipients such as CaO, Ca(OH)₂ or MgO, which are used to optimize the process.

In the entire process, pressure, temperature, time, atmosphere and further variables can be set, as clarified in FIG. 2 in the “Variation” box.

The crushing in the ISC takes place in particular with milling balls liable to wear, which preferably consist of zirconium oxide. Depending on the application, the milling ball sizes vary and possibly also the slot sizes in the milling basket, with the slot size being smaller than the smallest milling ball. Milling balls preferably have an average size of 0.1 to 30 mm, preferably approximately 1-2 mm, determined by the defined sieving and image analysis assessment.

If the starting material is provided in a suspension, in the ISC a surface (36) as smooth and turbulence-free as possible is created on the suspension (3) by diversion of the product flow by the flow breakers (6) on the container bottom, which prevents an undesired induction of air from the air into the suspension (3) during operation of the plant.

With continuous operation of the ISC, which is achieved by additional internals, a statistic factor for only one single dispersing/milling operation is defined. With this factor, the possible throughput rate can be determined.

The execution of the in situ synthesis crushing in the dry manner as well as in the wet manner can optionally be carried out in one step or in several steps, several steps in that the in situ synthesis crushing is carried out in several in situ synthesis crushers connected subsequently in a row or in a cascade.

With this milling process, in particular basic products with a defined particle size and a high, controlled reactivity can be produced, which preferably have an average particle size with a lower limit of 0.01 μm, preferably 0.05 μm, particularly preferably 0.1 μm and even more preferably 0.2 μm, and an upper limit of 50 μm, preferably 25 μm, particularly preferably 20 μm and even more preferably 10 μm. In this regard, the limits of the particles depend on the later use. The average particle size of the basic products is determined as described above in connection with the separation into the fine and finest fractions.

These basic products, designated in FIG. 2 as basic products 3+4, can directly be further used or be used for mixing with other basic products.

The particles obtained after the in situ crushing synthesis can be supplied as often as desired either to HFPI crushing with in situ separation or again to the in situ crushing synthesis in the ISC, as designated in FIG. 2 as “x-fold recycling” after the in situ crushing synthesis.

Furthermore, there is the option that the particles of the fine and finest fractions obtained in the pretreatment avoid the in situ synthesis crushing, as designated in FIG. 2 as “avoiding ISC”. The particles of the fine and finest fractions, which have avoided in situ synthesis crushing, are optionally united with the particles treated in the ISC and thus form the basic products 5+6 in FIG. 2.

The above-stated additives such as carbon dioxide or carbon dioxide containing gases or reagents can in turn optionally be added to the optionally united fractions consisting of the particles of the in situ synthesis crushing, which are optionally united with the particles of the fine and/or finest fraction, which is designated in FIG. 2 as “optional”.

With the particles or united fractions obtained in the above process, aqueous dispersions can be produced separately and optionally without air contact or air induction in that the basic products are fed into an aqueous medium. Furthermore, separating agents can additionally be added to the obtained fractions or to the dispersions containing the particles. Furthermore, these particles or the prepared dispersions can be preferably subjected to a subsequent milling process for further reduction of the particle size. These options are also illustrated in a box in FIG. 2.

To recycle the produced basic products in industrial applications there is furthermore the option to add additives, preferably citric acid or potassium chloride and to mix, further treat or further mill the basic products to obtain thus the basic products 7+8 of FIG. 2.

A possible drying of the particles produced according to the above method results in the basic product 9 of FIG. 2, which can be mixed, further processed and/or further crushed. The basic products 1-9 can, independent of each other, further be mixed with each other in any ratio and in any form to produce a basic product of the method according to the invention.

All the basic products shown in FIG. 2 or the mixture with any proportions thereof are optionally used directly in the building industry for ground stabilization as substitute for burnt lime. In particular, the basic product obtained from said fine fraction is used for this.

Furthermore, the basic products according to the invention are essentially used directly as alkalizing agents for instance instead of soda lye (soda lye substitute) in e.g. deinking processes, for the alkalization of fiber and wood substances and for the stabilization of wastewater purification plants or as alkaline adsorption agent instead of lime (DE 10 2005 029 500 A1). In particular, the basic product obtained from said finest fraction is used for this.

Furthermore, the basic products are essentially used directly as adsorption agent, as filler, in particular as paper filler, as pigment, as plaster, in composites/synthetics, in fiber plates, as binders and/or as jointing material.

One advantage of the present invention is that the production of the basic products is particularly energy-efficient. For instance, in the production of CaO-based components via the burnt lime process (PCC production via Ca(OH)₂) according to conventional methods approximately 1250-1300 kWh/t as well as approximately 200 kWh/t for the subsequent milling, i.e. in total approximately 1500 kWh/t, are necessary, whereas by comparison only 110 kWh/t are required for the basic product production according to the invention.

A further unexpected advantage of the invention is that particles with physical-chemical advantages are obtained, which cannot be obtained with conventional methods. For instance, new interior surfaces are formed for the produced particles due to an increase of the material diffusion by increasing the microporosity, in which water and other reactive substances such as e.g. CO₂ (dissolved or gaseous) can be diffused. Through processes such as hydration, carbonation, sulfation, etc. an increase in volume and interior disintegrations due to the volume pressure in the particles occur. Through these chemical reactions, an additional particle crushing of the starting material takes place.

The basic products produced by the invention thus have a defined formation of exterior and interior surfaces, the increased reactivity of which can furthermore be used by in situ synthesis and thus results in particles with increased quality.

The basic products produced according to the invention have e.g. an increased degree of whiteness vis-à-vis the conventional method of wet milling, which indicates that reactive and/or latent sites are exposed, which can be reacted with additives and reagents such as CO₂. A particular advantage of the method according to the invention is the production of basic products with defined particle size distribution for the definition of specific properties for basic or end products e.g. the definition of the paper properties (gloss, whiteness, opacity, printability, strengths, integration of the paper structure) or the definition of the surface structure for water absorption and setting of ground materials in ground stabilization.

A particular advantage is moreover that the increased reactivity, which is obtained in the precrushing of the starting materials e.g. in the HFPI crusher, can be used by the method according to the invention.

A further advantage of this invention is that an agglomerate or aggregate formation, which occurs in the crushing according to conventional methods with grinding units such as ball mills, does not take place or only takes place to a very minor extent. This provides technical advantages in the recycling process, since e.g. almost no machine downtimes are caused by deposition, cakings or by abrasive wear of the milling tool.

By preventing the agglomerate formation, basic products with a defined particle size, i.e. a defined average particle size and defined maximum particle size, are moreover obtained with the method according to the invention. When these basic products are reintroduced into industrial processes, they do not generate a disruption of the industrial process steps which occur e.g. with particles and agglomerates having a too large diameter.

Hereinbelow, unrestrictive examples are provided, which serve as clarification of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sketch of the principle of the in situ synthesis crusher that is suited for carrying out the method according to the invention.

FIG. 2 schematically shows possible workflows of the method according to the invention for the production of basic products.

FIG. 3 shows a test set-up of a plant for providing the starting material for the method according to the invention.

EMBODIMENT EXAMPLES In Situ Synthesis Crushing

According to FIG. 1, the particles of the starting material are subjected to crushing in an in situ synthesis crusher (1) (also ISC), with an additive for synthesis (32) being supplied directly into the milling zone of the ISC and foreign air induction during milling being prevented. This takes place in a container (1) of a ring chamber dispersing mill with slot lengths and widths defined depending on the product requirements, which is filled with the starting material (3) via the filler inlet (4). Owing to the rotation of a propeller (11), the starting material (3) is transported uniformly from the surface downwardly into the center. This product flow moves through the inlet tube (17) of the stator to directly before the dispersing disk (13), where it is deflected radially outwards (15) and is set into rotation by the blades (14) of the dispersing disk (13). At the edge of the dispersing disk (13), the product flow (24) absorbs the additives (32) and enables a synthesis between the additives (32) and the particles (28) carried along in the product flow. The product flow flows into the hollow space (22) of the ring chamber (21), with high shear forces occurring within the product flow in the transition from the rotating dispersing disk (13) to the stationary ring chamber (21). These shear forces on the one hand cause the dispersion of the product and the dissolution of present agglomerates and on the other hand ensure that the additive for synthesis can be optimally absorbed by the product suspension (3). In the hollow space (22) of the ring chamber (21) the actual milling takes place, by which individual product particles, which are caught between two milling balls clashing at high speed, are broken up. In part, the milling also takes place directly at the interior wall of the ring chamber (21), where particles (29) are hit by striking milling balls (27). The product is deflected radially outwards (26) by the flow (24) through the slots (25) in the ring chamber, where the flow direction is diverted again upwardly to the surface by the double conical container base (2). Due to repeated suction of the suspension (3) by the propeller (11), the cycle is kept running until the desired degree of milling of the particles (29) is achieved and the product is released.

Provision of the Starting Material by Upstream HFPI Crushing and In Situ Separation

The starting material ash is supplied from a silo (1) (hereinafter referring to FIG. 3) as starting material for temperature setting in an ash cooler. The ash is circulated with a blower in the ash cooler (2) and, if necessary, the temperature is reduced from approximately 140° C. to 70° C. by means of cooling water. The thus whirled up and cooled ash is supplied via a rotary feeder into the tube chain conveyor (5). The exhaust air is purified of finest particles via a reverse flow cartridge filter (3). The finest particles are supplied to the finest fraction (8), which is downstream of the crushing, via a valve.

The supply to the HFPI crusher (6) is carried out consistently via chain conveyor (5). The entire system is closed, pressure variations are compensated by a filter element at this point.

The crushing in the HFPI crusher (6) is carried out by means of counterrotating rotors with specific internals adapted according to the required basic or end product in an air atmosphere under high airflow.

The ash crushed in a non-contact manner is separated in a subsequent step into a fine fraction (8) (Cinerit) and a finest fraction (9) (Elurit) without a procedural gap, i.e. in situ. The separation into fine fraction and finest fraction is carried out via a cyclone. In the finest fraction (9), there is an air recycling (7) to the HFPI crusher. In the recirculation line, a further filter element is located which can be optionally connected to the existing exhaust air filter system and serves for pressure compensation.

Ash, which corresponds to the properties of the fine fraction and is yielded in a filter (3) during ash cooling, can optionally be directly supplied to the Cinerit container (8).

There is the option to supply the separated fractions to a silo (12) via an ash dispenser (10) and (11) and store these temporarily for further use. There is also the option to fill the fine fraction (Cinerit) and the finest fraction (Elurit) in separate silos (13) or (14) (Cinerit/Elurit).

Directly from the Cinerit (8) or Elurit (9) containers, the corresponding ash dispensers (10) or (11) or from the corresponding silos (12), (13) or (14), the fine and/or finest fraction is optionally suspended with water and dispersed in a dissolution plant, transported to the ring chamber dispersing mill (1) (hereinafter referring to FIG. 1) and filled into the ring chamber dispersing mill (1) via the filler inlet (4). The in situ synthesis crushing according to the invention follows.

Comparison of the Required Energy

The energy required to produce fillers/pigments according to the conventional burnt lime process is compared to the method according to the invention in Table 1.

The energy for the filler/pigment production according to the conventional burnt lime process is calculated via the sum for providing the basic product CaCO₃, which is stoichoimetrically calculated in relation to the CaO input, and the energy required for the wet milling of Ca(OH)₂ from CaO. The additional energy for transport and slaking is not included in the calculation.

The energy for the method according to the invention is calculated from the combination of the energy required for the low-energy pretreatment in the HFPI crusher and for the crushing in the in situ synthesis crusher according to the method according to the invention.

TABLE 1 Production of Fillers/Pigments Required Energy (90% < 2 m) kWh/t Ash Conventional burnt lime process 840 Method according to the invention as  80* combination of HFPI crusher and ISC (*the advantage of the lower amount of CO₂ required during synthesis is not included in the calculation)

Comparative Examples

In the following embodiment examples, ash is used as starting material. The ash, on which the following examples are based, is obtained in a 56 MW thermal power station with a fluidized-bed boiler by incineration of fiber residues (fibers yielded as loss in the waste paper recycling system) as well as waste wood and sawdust. Furthermore, removed color particles and sorted-out synthetic materials from the waste paper are contained in the material to be incinerated. The ash essentially consists of approximately 48% CaO (free lime content approximately 8%), 5% MgO, 14% Al₂O₃, 1% Na₂O, 0.2% K₂O, 35% SiO₂ and typical minor components of ash, as determined by X-ray fluorescence analysis.

Example 1 Ash Recycling According to the Method According to the Invention

The starting material ash is provided by the crushing in the HFPI crusher, which is carried out by means of counterrotating rotors with specific internals in an air atmosphere under high airflow. The in situ synthesis crushing is subsequently carried out according to the above-described method according to the invention in the presence of the additive for synthesis CO₂, added as 99.9% CO₂ gas (Linde gas cylinder).

Comparative Example 1

In Comparative Example 1, the ash recycling is carried out according to Example 1, with the difference that CO₂ is not present during the process.

Comparative Example 2

Ash Recycling According to Conventional Methods Recycling the ash according to conventional wet milling (MW 2 μm)

Comparative Example 3

In Comparative Example 3, the ash recycling is carried out according to Comparative Example 2, with the difference that CO₂ is present during the process.

Properties of the Produced Basic Products

The properties of the produced basic products were determined as follows:

The degree of whiteness was determined after reaction of the product with air and the CO₂ contained therein. The optical properties of the degree of whiteness R457 were determined by means of an L&W Elrepho/pulsed xenon lamp with D65 diffuse standard illuminant and 10° viewing.

Determination of the specific surface (BET) of solids according to DIN 66132, according to BET method, DIN EN ISO 18757 (previously: DIN EN 725-6) with AREA-meter II (Strohlein Instruments) according to Haul and Dümbgen.

The properties of the basic products from Examples 1 and 2 as compared to the basic product produced according to Comparative Examples 1 and 2 are listed in Table 2 and the properties of the particles, which are obtained via the conventional burnt lime process for the production of PCC (CaCO₃ from CaO, precipitated calcium carbonate), are compared.

TABLE 2 Compar- Compar- Compar- PCC from Reference ative ative ative burnt lime Example Example 1 Example 1 Example 2 Example 3 process BET [m²/g] 16.2 12 4.4 — 16.9 Degree of 85.4 74.5 71.1 78.2 95.5 whiteness D65/10° [%]

It is apparent from Table 2 that due to the method according to the invention starting from the starting material a significant increase of the specific surface and thus also an increase of the specific reactive surface is achieved, which is apparent here from the larger BET surface area and the increased degree of whiteness. It can moreover be seen that according to the method according to the invention basic products are produced, which have comparable properties as the PCC produced according to the conventional burnt lime process, however, as shown in Table 1, requiring significantly less energy.

Examples of Use Use of Ash as Soda Lye Substitute

In an aqueous dispersion, the ash that has been recycled using the method according to the invention can, as an alkaline component, replace the use of soda lye by using the alkali and alkaline earth oxide contents, e.g. in paper and wood production.

Use of Fine Particle Ash for Use in Ground Stabilization

The prerequisite for the use of ash in ground stabilization is a defined degree of particle size, which can only be achieved with the method according to the invention, but not with conventional methods such as ball mills.

The ash product according to the invention replaces burnt lime (CaO) here in ground stabilization, as a result of which it is possible to reduce the amount of energy required from conventionally 1391 kWh/t to only 80 kWh/t according to the invention.

Use of Ash as Filler/Pigment in Paper Production

The ash according to the invention can be used directly as filler in paper production by direct substitution of chalk/kaolin or indirectly by substitution of burnt lime in PCC processes (precipitated calcium carbonate). 

1. A method for producing basic products, comprising the following steps: i. providing the starting material in particle form, ii. mixing the particles of the starting material with at least one additive for synthesis, and iii. crushing the particles of the starting material, a modification of the particles by the added additives for synthesis taking place directly during crushing.
 2. The method according to claim 1, in which the produced basic product has an average particle size of 0.01 to 50 μm, in particular 0.05 to 50 μm.
 3. The method according to claims 1 and 2, in which the basic product is directly used as product, in particular for ground stabilization, as alkalizing agent, as soda lye substitute, as adsorption agent and/or as filler/pigment.
 4. The method according to one of claims 1 to 3, in which the starting material provided in step (i) is subjected to a pre-treatment in which the particles of the starting material are crushed and/or are separated into at least two fractions with different average particle sizes.
 5. The method according to claim 4, in which to provide the starting material the crushing of the particles of the starting material is carried out by pressure waves in the pre-treatment.
 6. The method according to claims 4 and 5, in which to provide the starting material the separation into at least a first fraction with an average particle size in the range from 0.1 to 8 μm and a second fraction with an average particle size in the range from 8 to 100 μm is carried out, and the at least two fractions are provided, independent of each other, as starting material in step (i).
 7. The method according to claims 1 to 6, in which the particles of the starting material in step (i) are provided in an aqueous slurry.
 8. The method according to one of claims 1 to 7, wherein the additive for synthesis, which is mixed with the starting material in step (ii), comprises one or more components selected from gases, aerosols, liquids and solids which comprise carbon dioxide, hydrogen fluoride, hydrogen carbonate, hydrogen bicarbonate, alkylalkoxysilanes or a mixture thereof.
 9. The method according to one of claims 1 to 8, wherein in at least one of the steps (i) to (iii) one or more additives selected from citric acid, polyacrylates, polyphosphates, polycarbonates, alcohols, in particular ethanol, isopropanols, alkoxypropanols, ketones, in particular acetone, amines, in particular triethylamine, silanes and siloxanes in benzine or isoparrafin, sulfuric acid, sulfates, in particular lignosulfates, alums, in particular aluminium sulfate, phosphoric acid, phosphates, soluble metallic salts, calcium oxide, calcium hydroxide and magnesium oxide are added.
 10. A dispersion produced by dispersing the basic product produced according to the method according to one of claims 1 to 9 in a dispersing medium. 